A side mounted vehicle rear view mirror is normally pivotally mounted to a vehicle mounting bracket so that it can be forwardly or rearwardly rotated relative to the vehicle. In an operative or in-use position it is located laterally of the vehicle body and in a folded or parked position is located approximately parallel to the side of the vehicle so as to prevent damage to the mirror and mirror housing. Such a folded position is useful when the vehicle is parked on narrow roadways or being taken through a car wash.
Motorised versions which fold mirrors in the manner described above are referred to as power fold mirrors and can be arranged with appropriate control electronics to move to a folded position when a button is pressed or upon the vehicle's ignition being turned off or alternatively the gear selector being placed in the parked position.
It is typical at this time for the motor used to drive the folding mechanism to be provided power until the current driving the motor is raised substantially above normal levels (over current) for a predetermined period of time. This can result from the mirror head coming against a stop. This manner of motor control is cheap to design, but not necessarily cheap to build and typically needs to include expensive transient suppression components. An alternative is to use expensive and potentially unreliable limit switches.
Furthermore, periods of over current are an undesirable feature of prior power fold mirror designs as this can ultimately lessen the life of the electric motor and its associated drive train components or can cause unexpected failure. Yet furthermore, as the effects of spurious electromagnetic (EM) emissions are sometimes unpredictable, especially upon vehicle electronic systems, it is advantageous to eliminate or keep to an acceptable minimum this type of emission.
It is also typical that the motor used to drive powered mirrors are direct current (d.c.) motors which require a specific polarity of current to drive them in a desired direction and this tends to complicate the design of typical motor drive circuits.
It is an aim of this invention to eliminate or reduce the abovementioned problems.